Add missing hasMore to pgUnionAll

graphile · May 23, 2023 · ab106b8 · ab106b8
1 parent 26b3f68
commit ab106b8
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Showing 2 changed files with 39 additions and 13 deletions.
diff --git a/grafast/dataplan-pg/src/steps/pgPageInfo.ts b/grafast/dataplan-pg/src/steps/pgPageInfo.ts
@@ -14,7 +14,7 @@ import {
 import type { PgCursorStep } from "./pgCursor.js";
 import type { PgSelectParsedCursorStep, PgSelectStep } from "./pgSelect.js";
 import { PgSelectSingleStep } from "./pgSelectSingle.js";
-import type { PgUnionAllStep } from "./pgUnionAll.js";
+import type { PgUnionAllSingleStep, PgUnionAllStep } from "./pgUnionAll.js";
 
 /*
  * **IMPORTANT**: see pgPageInfo.md for reasoning behind decisions made in this file
@@ -95,12 +95,14 @@ export class PgPageInfoStep<
     const lastExists = last && !last.evalIs(null) && !last.evalIs(undefined);
     if (firstExists && !lastExists) {
       const nodePlan = (
-        $connection as ConnectionStep<
-          any,
-          PgSelectParsedCursorStep,
-          PgSelectStep<any>,
-          any
-        >
+        $connection as
+          | ConnectionStep<
+              any,
+              PgSelectParsedCursorStep,
+              PgSelectStep<any>,
+              any
+            >
+          | ConnectionStep<any, PgSelectParsedCursorStep, PgUnionAllStep, any>
       ).cloneSubplanWithPagination();
       return nodePlan.hasMore();
     } else {
@@ -132,12 +134,19 @@ export class PgPageInfoStep<
     const lastExists = last && !last.evalIs(null) && !last.evalIs(undefined);
     if (lastExists && !firstExists) {
       const nodePlan = (
-        $connection as ConnectionStep<
-          PgSelectSingleStep<any>,
-          PgSelectParsedCursorStep,
-          PgSelectStep<any>,
-          PgSelectSingleStep<any>
-        >
+        $connection as
+          | ConnectionStep<
+              PgSelectSingleStep<any>,
+              PgSelectParsedCursorStep,
+              PgSelectStep<any>,
+              PgSelectSingleStep<any>
+            >
+          | ConnectionStep<
+              PgUnionAllSingleStep,
+              PgSelectParsedCursorStep,
+              PgUnionAllStep,
+              PgUnionAllSingleStep
+            >
       ).cloneSubplanWithPagination();
       return nodePlan.hasMore();
     } else if (

diff --git a/grafast/dataplan-pg/src/steps/pgUnionAll.ts b/grafast/dataplan-pg/src/steps/pgUnionAll.ts
@@ -78,6 +78,12 @@ const EMPTY_ARRAY: ReadonlyArray<any> = Object.freeze([]);
 const hash = (text: string): string =>
   createHash("sha256").update(text).digest("hex").slice(0, 63);
 
+// Constant functions so lambdas can be optimized
+function listHasMore(list: any | null | undefined) {
+  return list?.hasMore || false;
+}
+listHasMore.isSyncAndSafe = true; // Optimization
+
 function parseCursor(cursor: string | null) {
   if (cursor == null) {
     // This throw should never happen, so we can still be isSyncAndSafe.
@@ -965,6 +971,17 @@ on (${sql.indent(
     }
   }
 
+  /**
+   * Someone (probably pageInfo) wants to know if there's more records. To
+   * determine this we fetch one extra record and then throw it away.
+   */
+  public hasMore(): ExecutableStep<boolean> {
+    this.fetchOneExtra = true;
+    // HACK: This is a truly hideous hack. We should solve this by having this
+    // plan resolve to an object with rows and metadata.
+    return lambda(this, listHasMore);
+  }
+
   public placeholder($step: PgTypedExecutableStep<any>): SQL;
   public placeholder($step: ExecutableStep, codec: PgCodec): SQL;
   public placeholder(